Touch sensitive displays, e.g., touch screens, are very useful in applications where a user can input commands and data directly on a display. Common applications for touch screens include consumer products such as cellular telephones and user interfaces for industrial process control. Depending on their specific applications, these touch sensitive displays are commonly used in devices ranging from small handheld PDAs, to medium sized tablet computers, to large pieces of industrial equipment.
It is often convenient to be able to input and output data to and from the user on the same display. Unlike a dedicated input device such as a keypad with discrete well-defined keys, most touch sensitive displays are generally flat. As a result, touch sensitive screens do not provide any tactile guidance for one or more control “buttons”. Instead, touch sensitive displays rely on visual guidance for user input.
Hence a serious drawback of touch sensitive displays is its inherent difficulty to input data accurately because adjacent buttons are not distinguishable by feel. Wrongly entered key strokes are common and the user is forced to keep his or her eyes on the display. The importance of tactile guidance is readily apparent in the competition between the Apple iPhone and the BlackBerry 8800. With a limited size, the mobile phones prior to this invention could include either a large screen or tactile buttons. With this invention, mobile phones and other suitable electronic devices can include both.